/**
 * Tiny, dependency-free test helpers for driving serial devices — shared by the
 * library's own conformance suite, the {@link SerialClient}, and consumers' app
 * tests. Free of `jest` and `react-native`, so they run under any test runner
 * and on a real device (e.g. an on-device Self-Test screen).
 */
/** Throw `message` if `condition` is falsy. */
export declare function assert(condition: unknown, message: string): asserts condition;
/** Throw if `actual !== expected`, including both values in the message. */
export declare function assertEqual<T>(actual: T, expected: T, message: string): void;
/** Byte-for-byte equality of two sequences. */
export declare function bytesEqual(a: ArrayLike<number>, b: ArrayLike<number>): boolean;
/** What {@link assertRejects} may additionally check about the thrown error. */
export type RejectionExpectation = {
    name?: string;
    type?: new (...args: never[]) => Error;
    message?: string | RegExp;
};
/** Assert `fn()` rejects (optionally matching the error name/type/message). */
export declare function assertRejects(fn: () => Promise<unknown>, message: string, expected?: RejectionExpectation): Promise<void>;
/** Normalise any thrown value into a `"Name: message"` string. */
export declare function errorMessage(e: unknown): string;
/** Reject if `promise` doesn't settle within `ms`; `label` names it on timeout. */
export declare function withTimeout<T>(promise: Promise<T>, ms: number, label: string): Promise<T>;
/** The slice of `ReadableStreamDefaultReader` the helpers need. */
export type ByteReader = {
    read(): Promise<{
        done: boolean;
        value?: Uint8Array;
    }>;
};
/** Read exactly `count` bytes from a reader (accumulating chunks), with a timeout. */
export declare function readBytes(reader: ByteReader, count: number, timeoutMs?: number): Promise<number[]>;
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